Using a simple ASCII file of X,Y values, build a ds9 regions file for marking circles of a user-specified size and color.

% xy2circ_reg listXY 20.0 cyan  
physical
circle(423.28889,321.6,20.0) # color=cyan
circle(645.58889,865,20.0) # color=cyan
circle(1276.8111,469.8,20.0) # color=cyan
circle(672.48444,951.1755,20.0) # color=cyan
circle(576.97778,78.4422,20.0) # color=cyan
circle(211.96667,1175.1222,20.0) # color=cyan
circle(1510.0889,1144.933,20.0) # color=cyan

A good way to make the file for use in ds9:
% xy2circ_reg listXY 20.0 cyan >in.reg 

If you have the ds9 image viewer ready, then to overplot the file:
% cat in.reg | xpaset ds9 regions -format ds9 

A good place to demo this sort of thing is in:
 $tdata/T_runs/clip_1/ex1_boxcen

Use the listIN file as the input XY file.